Tanning hides and skins



war-cr m ERNEST WYNDHAM MERRY, or SHEFFIEL ENGLAND, AssIeNon 'ro PYnorAN LEATHER CORPORATION, OF,WILMII\1 'GTON, DELAWARE, A CORPORATION or DELAWARE.

No Drawing.

a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to the tanning of hides and skins, and more particularly to a process wherein the advantages of chrome tannage are combined with those incident to the useof a mixture of soluble pyrophosphate and alum as the principal tanning agents.

The objectof my invention therefore is to produce a desirable and highly satisfactory leather at a relatively slight cost Which is resistant to heat and moisture and is adaptable to a wide variety The use of a soluble pyrophosphate'in connection with alum and salt has been described in Letters Patent #1,089,150 and #l,191,527.' According to the process described therein, the hides are subjected after the usual preliminary cleansing and unhairing treatment, to solutions comprising alum, common salt, and sodium pyrophosphate under specified conditions, to convert the hide into a superior quality of leather. For certain purposes it is desirable that the leather exhibit an extreme resistance to heat and moisture and I have discovered that a leather adapted to such special purposes may be economically manufactured through the combination of pyrophosphate tanning and chrome tanning as hereinafter described.

It is possible to accomplish this desirable result, either by subjecting the hides to a combined solution containing the essential ingredients-to accomplish both the pyrophosphate and chrome tanning, or by first subjecting the hides to a pyroposphate tanning and subsequently treating them with a chrome-tanning liquor, whereby the desirable features of-chrome tannage are imparted to the resulting leather.

In carrying out my invention, the hides or skins are preferably subjected to the usual washing, liming, unhairing, and fleshing op- Sp'ecification of Letters Patent.

residing of purposesls and any soluble alumin TANNING nines AND SKINS.

Application filed February 11,,1919. Serial No. 2?6,341.

erations, after which they'may be bated and finally washed in water or suitable cleansmama May 9,1922;

mg solutions until throughly clean and in i suitable condition for the actual tanning V operations. The details of the preliminary treatment form 110, part of my present in' ventlon, and may be widely varied in accordance withv established practicein tan- I yards or otherwise. a

The prepared hides'are then subjected in a suitable receptacle for example, a pit, drum,

wheel, or paddle, to the action of a tanning solutlonwh ch includes a suitable proportion of a soluble pyrophosphate, a soluble aluminum salt, and a suitable material such a as sodium chloride or common salt, for overcoming the astringent action o-fthe aluminum saltupon the h1de,whereby'it'is maintained in a porous condition to assimilate I the active tanning agents Preferably,.so

dium pyrophosphate, ammonia alum, and

common saltare employed although other um salt may be adused. For example, sodaalum, aluminum sulphate, or

vantageously alum, potash aluminunr chloride may be substituted for the ammonia alum.

According to one modification of the procoluble 'pyrophosph'ates may be substituted ceptacle duringthe tanning operation. The I chrome liquor employedmay be any ofv the; usual liquors readily obtainable, in the- -market and commonly employed in chrome. I

tannage. Such a liquor for example, may

include chrome alum "Which has'been rendered basic by the addition ofa suitable alkali such as sodium carbonate, but it is to be understood that my invention contemplates the employment of any of tllG'llSllEtl and Well. known single bath chrome tanningagents of whleh there are a number avallable.

ticularly the proportion of'the chrome liquor The proportions ofythe various ingredients of the tanning solutlon, and parto the pyrophosphate mixture will depend] entirely upon the particular purpose to be accomplished, aswell as upon the character of the material under treatment. The hide after remaining innthe combined tanningsolution during a sufiicient time 1nterval to accomplish thorough tanning, is withdrawn and treated in accordance with the usual practice to produce finished leather.

According to another mooification or my invention. the hide is first subjected under suitable conditions to a tannin? solution consisting of a soluble pyrophosphate, soluble aluminum salt, and common salt, in a suitable receptacle as above described, until the tanning of the hide is practically completed. he chrome liquor is then added directly to the spent solution in the receptacle and re nains in contact with the hide or a suliicicnt period to impart the dcsirec J qualities thereto.

The concentration of the solution employed th reference the SGT-O l salts conta herein, may vary somewhat depending upon the particular character of the hide treated. Preferably the proportion of pyrophcsphate to the alum is maintaii ed at a relatively low ratio which may, however vary from 1 to 1:10. The higher proportions of pyrophosphate are desirable where the hides are heavy and oil close texture, and the lower proportions are desirable in the treatment ot hides and skins of relatively light weight and loose texture. For general purposes the range of relative proportions of ah n to pyrophosphatc may be limited so that the slum exceeds 5 but does not exceed '7 times the w-ight of pyrophes phate. The proportion of standard chrome liquor will vary from a fraction of one per cent upward to eight per cent of the weight of the hide substance, but the higher p' centages will rarely be necesssary inasmuch. as the entire purpose of the chrome liquor is to impart certain desirable qualities to the leather which has been alreat y tanned by the pyrophosphate solution.

The process, whether practiced by the gradual addition or" the chrome liquor to the pyrophosphate solution, or by the addition of the chrome liquor after completion or" the pyrophospha-te tannagecresults in a product having the desirable charactei i tics imparted by both methods of tanning and is completed at a relatively low cost, compared with the ordinary application of: chrome tannage. he product for en. nple will be substantially moisture-proof and heat-resistant and may be subjected therefore to certain manufacturing operations. whereby a more delicate leather would be injured v through the application of: heat or moisture bet-weeii one and c1 to the finished product, Moisture proof and heat resistant leathers have moreover, many applications in the arts, which the product oi the process herein described is well adapted to meet.

In the foregoing it will be readily understood that l have perfected an improved process of treating hides and skins whereby certain desirable results are accomplished and that variations may be made in the process, as well as in the ingredients employed, without departing from the invention or sacrificing any of the material advantages thereof.

1 claim:

1. A method of combined tans-age of hides and skins, to produce heat and moisture resistantleather, which comprises subjecting the hide to the tanning action of a solution including a soluble pyrophosphate and a soluble aluminum salt inrelatiye proportions varying from 11 i to 1:10, and of a chrome liquor in limited quantity, sufficient only to impart the characteristics of chro he tannage to the leather.

2. A method of combined ,tanuage oi" hides and skins to )roduce heat and moisture re sistant leatl'ier. which comprises the successiye treatment of the hide with solutions ineluding a soluble pyrophosphate and including a chrome liquor, the latter being employed in proportions Varying from one to eight per cent of the weight of the'hide sul stance treated.

' A. method of combined tannage of hides ainl skins to produce heatand moisture resistant leather, which comprises suliiject-ing the hide to the tanning action of a solution of soluble pyi'ophosphate and a soluble aluminum salt, and adding a chrome liquor to the solution during the tanning operation in proportions varying between one and eight per cent of the weight of the hide treated.

l. Ll methodot combined tannage 0t hides (l. sistant leather. which cou'iprises subjecting l e hide to the tanning action of a solution soluble pyrophesphate and soluble salt. and gradually chrome liquor to the U solution d tanning operation p1 oportions varying lt per cent oi the weighto'j the hide treated. H

In. tEEStliUODY whereof: l atli; my signature.

ERNEST lVYNDHAli'l MERE Y nus to produce heat and moisture re 

